Add support for persistent file access in apps.

apps/saved_files_service.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef APPS_SAVED_FILES_SERVICE_H_
+#define APPS_SAVED_FILES_SERVICE_H_
+
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "base/files/file_path.h"
+#include "base/gtest_prod_util.h"
+#include "base/stl_util.h"
+#include "chrome/browser/profiles/profile_keyed_service.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+class SavedFilesServiceUnitTest;
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, EvictionTest);
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, SequenceNumberCompactionTest);
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest,
+                     SequenceNumberCompactionFirstAboveOneTest);
+
+namespace extensions {
+class Extension;
+}  // namespace extensions
+
+namespace apps {
+
+// Represents a file entry that a user has given an app permission to
+// access. Intended to be persisted to disk (in the Preferences file), so should
+// remain serializable.
+struct SavedFileEntry {
+  SavedFileEntry()
+      : writable(false),
+        sequence_number(0) {}
+
+  SavedFileEntry(const std::string& id,
+                 const base::FilePath& path,
+                 bool writable,
+                 int sequence_number)
+      : id(id),
+        path(path),
+        writable(writable),
+        sequence_number(sequence_number) {}
+
+  // The opaque id of this file entry.
+  std::string id;

[koz (OOO until 15th September), 2013/05/20 05:33:51]

nit: newlines between these fields.

[Sam McNally, 2013/05/20 07:13:33]

Done.

+  // The path to a file entry that an extension had permission to access.
+  base::FilePath path;
+  // Whether or not an extension had write access to a file entry.
+  bool writable;
+  // The sequence number in the LRU of the file entry.
+  int sequence_number;
+};
+
+class SavedFilesService : public ProfileKeyedService,
+                          public content::NotificationObserver {
+ public:
+  explicit SavedFilesService(Profile* profile);
+  virtual ~SavedFilesService();
+
+  static SavedFilesService* Get(Profile* profile);
+
+  // Adds a file entry to be retained, but does not add it to the queue of
+  // entries to be retained between app runs.
+  void RetainFileEntry(const std::string& extension_id,

[koz (OOO until 15th September), 2013/05/20 05:33:51]

Sounds like SavedFilesService has two sets of files - those that will be
retained between runs and those that are only retained until the extension is
suspended. I think exposing this in the method names of this class would make
its usage much clearer. What do you think of the following renames:

RetainFileEntry() -> RetainFileUntilAppSuspend()
MoveEntryToFrontOfQueue() -> RetainFilePermanently()
FlushRetainedEntries() -> ReleaseNonPermanentFiles()

I think it's enough to note in comments that "permanent" is a relative term
here.

[Matt Giuca, 2013/05/20 05:41:05]

I don't like RetainFilePermanently because it doesn't imply that it will bring
the file to the front of the queue. Otherwise agree.

[Sam McNally, 2013/05/20 07:13:33]

Done.

+                       const std::string& id,
+                       const base::FilePath& file_path,
+                       bool writable);
+
+  // Moves the file entry with the specified |id| to the front of the LRU,
+  // evicting the least recently used entry if the queue is full and the entry
+  // specified by |id| is not already in the queue.
+  void MoveEntryToFrontOfQueue(const std::string& extension_id,
+                               const std::string& id);
+
+  // Returns whether the file entry with the given |id| is retained. This does
+  // not consider whether or not the file entry is in the queue.
+  bool IsRetained(const std::string& extension_id, const std::string& id);
+
+  // Stores the file entry with the specified |id| in |out| and returns true if
+  // the file entry is retained or returns false.
+  bool GetFileEntry(const std::string& extension_id,
+                    const std::string& id,
+                    SavedFileEntry* out);
+
+  // Returns all retained file entries.
+  std::vector<SavedFileEntry> GetAllFileEntries(
+      const std::string& extension_id);
+
+  // Clears all retained files that are not in the retained files queue. If the
+  // app does not have the fileSystem.retainFiles permission, the queue will
+  // also be cleared.
+  void ClearRetainedFiles(const extensions::Extension* extension);

[Matt Giuca, 2013/05/20 01:32:57]

This name is not appropriate. Because it basically clears everything OTHER than
the retained files queue. Think of a better name.

[Sam McNally, 2013/05/20 04:25:20]

Done.

+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest, EvictionTest);
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest,
+                           SequenceNumberCompactionTest);
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest,
+                           SequenceNumberCompactionFirstAboveOneTest);
+  friend class ::SavedFilesServiceUnitTest;
+
+  class SavedFiles;
+
+  // content::NotificationObserver.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+  SavedFiles* GetOrInsert(const std::string& extension_id);
+
+  void Cleanup(const std::string& extension_id);
+
+  static void SetMaxSequenceNumberForTest(int max_value);
+  static void ClearMaxSequenceNumberForTest();
+  static void SetLruSizeForTest(int size);
+  static void ClearLruSizeForTest();
+
+  std::map<std::string, SavedFiles*> extension_id_to_saved_files_;
+  STLValueDeleter<std::map<std::string, SavedFiles*> >
+      extension_id_to_saved_files_deleter_;
+  content::NotificationRegistrar registrar_;
+  Profile* profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(SavedFilesService);
+};
+
+}  // namespace apps
+
+#endif  // APPS_SAVED_FILES_SERVICE_H_